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data-v-6b87e69f><!--[--><!--]--><!----><main class="main" data-v-6b87e69f><div style="position:relative;" class="vp-doc _largeFrontEnd_flutter_chapter3_input_and_form" data-v-6b87e69f><div><h1 id="_3-5-输入框及表单" tabindex="-1">3.5 输入框及表单 <a class="header-anchor" href="#_3-5-输入框及表单" aria-label="Permalink to &quot;3.5 输入框及表单&quot;">​</a></h1><p>Material 组件库中提供了输入框组件<code>TextField</code>和表单组件<code>Form</code>。下面我们分别介绍一下。</p><h2 id="_3-5-1-textfield" tabindex="-1">3.5.1 TextField <a class="header-anchor" href="#_3-5-1-textfield" aria-label="Permalink to &quot;3.5.1 TextField&quot;">​</a></h2><p><code>TextField</code>用于文本输入，它提供了很多属性，我们先简单介绍一下主要属性的作用，然后通过几个示例来演示一下关键属性的用法。</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#F97583;">const</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">({</span></span>
<span class="line"><span style="color:#E1E4E8;">  ...</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;"> controller, </span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">FocusNode</span><span style="color:#E1E4E8;"> focusNode,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;"> decoration </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">const</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(),</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">TextInputType</span><span style="color:#E1E4E8;"> keyboardType,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">TextInputAction</span><span style="color:#E1E4E8;"> textInputAction,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">TextStyle</span><span style="color:#E1E4E8;"> style,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">TextAlign</span><span style="color:#E1E4E8;"> textAlign </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextAlign</span><span style="color:#E1E4E8;">.start,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">bool</span><span style="color:#E1E4E8;"> autofocus </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">false</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">bool</span><span style="color:#E1E4E8;"> obscureText </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">false</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">int</span><span style="color:#E1E4E8;"> maxLines </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">1</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">int</span><span style="color:#E1E4E8;"> maxLength,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">this</span><span style="color:#E1E4E8;">.maxLengthEnforcement,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">ToolbarOptions</span><span style="color:#F97583;">?</span><span style="color:#E1E4E8;"> toolbarOptions,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">ValueChanged</span><span style="color:#E1E4E8;">&lt;</span><span style="color:#79B8FF;">String</span><span style="color:#E1E4E8;">&gt; onChanged,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">VoidCallback</span><span style="color:#E1E4E8;"> onEditingComplete,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">ValueChanged</span><span style="color:#E1E4E8;">&lt;</span><span style="color:#79B8FF;">String</span><span style="color:#E1E4E8;">&gt; onSubmitted,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">List</span><span style="color:#E1E4E8;">&lt;</span><span style="color:#79B8FF;">TextInputFormatter</span><span style="color:#E1E4E8;">&gt; inputFormatters,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">bool</span><span style="color:#E1E4E8;"> enabled,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">this</span><span style="color:#E1E4E8;">.cursorWidth </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">2.0</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">this</span><span style="color:#E1E4E8;">.cursorRadius,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">this</span><span style="color:#E1E4E8;">.cursorColor,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">this</span><span style="color:#E1E4E8;">.onTap,</span></span>
<span class="line"><span style="color:#E1E4E8;">  ...</span></span>
<span class="line"><span style="color:#E1E4E8;">})</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#D73A49;">const</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">({</span></span>
<span class="line"><span style="color:#24292E;">  ...</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;"> controller, </span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">FocusNode</span><span style="color:#24292E;"> focusNode,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;"> decoration </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">const</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(),</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">TextInputType</span><span style="color:#24292E;"> keyboardType,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">TextInputAction</span><span style="color:#24292E;"> textInputAction,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">TextStyle</span><span style="color:#24292E;"> style,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">TextAlign</span><span style="color:#24292E;"> textAlign </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextAlign</span><span style="color:#24292E;">.start,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">bool</span><span style="color:#24292E;"> autofocus </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">false</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">bool</span><span style="color:#24292E;"> obscureText </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">false</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">int</span><span style="color:#24292E;"> maxLines </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">1</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">int</span><span style="color:#24292E;"> maxLength,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">this</span><span style="color:#24292E;">.maxLengthEnforcement,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">ToolbarOptions</span><span style="color:#D73A49;">?</span><span style="color:#24292E;"> toolbarOptions,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">ValueChanged</span><span style="color:#24292E;">&lt;</span><span style="color:#005CC5;">String</span><span style="color:#24292E;">&gt; onChanged,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">VoidCallback</span><span style="color:#24292E;"> onEditingComplete,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">ValueChanged</span><span style="color:#24292E;">&lt;</span><span style="color:#005CC5;">String</span><span style="color:#24292E;">&gt; onSubmitted,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">List</span><span style="color:#24292E;">&lt;</span><span style="color:#005CC5;">TextInputFormatter</span><span style="color:#24292E;">&gt; inputFormatters,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">bool</span><span style="color:#24292E;"> enabled,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">this</span><span style="color:#24292E;">.cursorWidth </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">2.0</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">this</span><span style="color:#24292E;">.cursorRadius,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">this</span><span style="color:#24292E;">.cursorColor,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">this</span><span style="color:#24292E;">.onTap,</span></span>
<span class="line"><span style="color:#24292E;">  ...</span></span>
<span class="line"><span style="color:#24292E;">})</span></span></code></pre></div><ul><li><p><code>controller</code>：编辑框的控制器，通过它可以设置/获取编辑框的内容、选择编辑内容、监听编辑文本改变事件。大多数情况下我们都需要显式提供一个<code>controller</code>来与文本框交互。如果没有提供<code>controller</code>，则<code>TextField</code>内部会自动创建一个。</p></li><li><p><code>focusNode</code>：用于控制<code>TextField</code>是否占有当前键盘的输入焦点。它是我们和键盘交互的一个句柄（handle）。</p></li><li><p><code>InputDecoration</code>：用于控制<code>TextField</code>的外观显示，如提示文本、背景颜色、边框等。</p></li><li><p><code>keyboardType</code>：用于设置该输入框默认的键盘输入类型，取值如下：</p><table><thead><tr><th>TextInputType枚举值</th><th>含义</th></tr></thead><tbody><tr><td>text</td><td>文本输入键盘</td></tr><tr><td>multiline</td><td>多行文本，需和maxLines配合使用(设为null或大于1)</td></tr><tr><td>number</td><td>数字；会弹出数字键盘</td></tr><tr><td>phone</td><td>优化后的电话号码输入键盘；会弹出数字键盘并显示“* #”</td></tr><tr><td>datetime</td><td>优化后的日期输入键盘；Android上会显示“: -”</td></tr><tr><td>emailAddress</td><td>优化后的电子邮件地址；会显示“@ .”</td></tr><tr><td>url</td><td>优化后的url输入键盘； 会显示“/ .”</td></tr></tbody></table></li><li><p><code>textInputAction</code>：键盘动作按钮图标(即回车键位图标)，它是一个枚举值，有多个可选值，全部的取值列表读者可以查看API文档，下面是当值为<code>TextInputAction.search</code>时，原生Android系统下键盘样式如图3-18所示：</p><p><img src="/assets/3-18.e52ace64.png" alt="图3-18"></p></li><li><p><code>style</code>：正在编辑的文本样式。</p></li><li><p><code>textAlign</code>: 输入框内编辑文本在水平方向的对齐方式。</p></li><li><p><code>autofocus</code>: 是否自动获取焦点。</p></li><li><p><code>obscureText</code>：是否隐藏正在编辑的文本，如用于输入密码的场景等，文本内容会用“•”替换。</p></li><li><p><code>maxLines</code>：输入框的最大行数，默认为1；如果为<code>null</code>，则无行数限制。</p></li><li><p><code>maxLength</code>和<code>maxLengthEnforcement</code> ：<code>maxLength</code>代表输入框文本的最大长度，设置后输入框右下角会显示输入的文本计数。<code>maxLengthEnforcement</code>决定当输入文本长度超过<code>maxLength</code>时如何处理，如截断、超出等。</p></li><li><p><code>toolbarOptions</code>：长按或鼠标右击时出现的菜单，包括 copy、cut、paste 以及 selectAll。</p></li><li><p><code>onChange</code>：输入框内容改变时的回调函数；注：内容改变事件也可以通过<code>controller</code>来监听。</p></li><li><p><code>onEditingComplete</code>和<code>onSubmitted</code>：这两个回调都是在输入框输入完成时触发，比如按了键盘的完成键（对号图标）或搜索键（🔍图标）。不同的是两个回调签名不同，<code>onSubmitted</code>回调是<code>ValueChanged&lt;String&gt;</code>类型，它接收当前输入内容做为参数，而<code>onEditingComplete</code>不接收参数。</p></li><li><p><code>inputFormatters</code>：用于指定输入格式；当用户输入内容改变时，会根据指定的格式来校验。</p></li><li><p><code>enable</code>：如果为<code>false</code>，则输入框会被禁用，禁用状态不能响应输入和事件，同时显示禁用态样式（在其<code>decoration</code>中定义）。</p></li><li><p><code>cursorWidth</code>、<code>cursorRadius</code>和<code>cursorColor</code>：这三个属性是用于自定义输入框光标宽度、圆角和颜色的。</p></li></ul><h3 id="_1-示例-登录输入框" tabindex="-1">1. 示例：登录输入框 <a class="header-anchor" href="#_1-示例-登录输入框" aria-label="Permalink to &quot;1. 示例：登录输入框&quot;">​</a></h3><h4 id="_1-布局" tabindex="-1">1）布局 <a class="header-anchor" href="#_1-布局" aria-label="Permalink to &quot;1）布局&quot;">​</a></h4><p>我们实现一个登录表单：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">Column</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">  children</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">&lt;</span><span style="color:#79B8FF;">Widget</span><span style="color:#F97583;">&gt;</span><span style="color:#E1E4E8;">[</span></span>
<span class="line"><span style="color:#E1E4E8;">    </span><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      autofocus</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">true</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">      decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">        labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;用户名&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">        hintText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;用户名或邮箱&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">        prefixIcon</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Icon</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Icons</span><span style="color:#E1E4E8;">.person)</span></span>
<span class="line"><span style="color:#E1E4E8;">      ),</span></span>
<span class="line"><span style="color:#E1E4E8;">    ),</span></span>
<span class="line"><span style="color:#E1E4E8;">    </span><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">        labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;密码&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">        hintText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;您的登录密码&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">        prefixIcon</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Icon</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Icons</span><span style="color:#E1E4E8;">.lock)</span></span>
<span class="line"><span style="color:#E1E4E8;">      ),</span></span>
<span class="line"><span style="color:#E1E4E8;">      obscureText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">true</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">    ),</span></span>
<span class="line"><span style="color:#E1E4E8;">  ],</span></span>
<span class="line"><span style="color:#E1E4E8;">);</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">Column</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">  children</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">&lt;</span><span style="color:#005CC5;">Widget</span><span style="color:#D73A49;">&gt;</span><span style="color:#24292E;">[</span></span>
<span class="line"><span style="color:#24292E;">    </span><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      autofocus</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">true</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">      decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">        labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;用户名&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">        hintText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;用户名或邮箱&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">        prefixIcon</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Icon</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Icons</span><span style="color:#24292E;">.person)</span></span>
<span class="line"><span style="color:#24292E;">      ),</span></span>
<span class="line"><span style="color:#24292E;">    ),</span></span>
<span class="line"><span style="color:#24292E;">    </span><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">        labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;密码&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">        hintText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;您的登录密码&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">        prefixIcon</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Icon</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Icons</span><span style="color:#24292E;">.lock)</span></span>
<span class="line"><span style="color:#24292E;">      ),</span></span>
<span class="line"><span style="color:#24292E;">      obscureText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">true</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">    ),</span></span>
<span class="line"><span style="color:#24292E;">  ],</span></span>
<span class="line"><span style="color:#24292E;">);</span></span></code></pre></div><p>运行后，效果如图3-19所示：</p><p><img src="/assets/3-19.8d291267.png" alt="图3-19"></p><h4 id="_2-获取输入内容" tabindex="-1">2）获取输入内容 <a class="header-anchor" href="#_2-获取输入内容" aria-label="Permalink to &quot;2）获取输入内容&quot;">​</a></h4><p>获取输入内容有两种方式：</p><ol><li>定义两个变量，用于保存用户名和密码，然后在<code>onChange</code>触发时，各自保存一下输入内容。</li><li>通过<code>controller</code>直接获取。</li></ol><p>第一种方式比较简单，不在举例，我们来重点看一下第二种方式，我们以用户名输入框举例：</p><p>定义一个<code>controller</code>：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#6A737D;">//定义一个controller</span></span>
<span class="line"><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;"> _unameController </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;">();</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#6A737D;">//定义一个controller</span></span>
<span class="line"><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;"> _unameController </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;">();</span></span></code></pre></div><p>然后设置输入框controller：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">    autofocus</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">true</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">    controller</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> _unameController, </span><span style="color:#6A737D;">//设置controller</span></span>
<span class="line"><span style="color:#E1E4E8;">    ...</span></span>
<span class="line"><span style="color:#E1E4E8;">)</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">    autofocus</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">true</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">    controller</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> _unameController, </span><span style="color:#6A737D;">//设置controller</span></span>
<span class="line"><span style="color:#24292E;">    ...</span></span>
<span class="line"><span style="color:#24292E;">)</span></span></code></pre></div><p>通过controller获取输入框内容</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#B392F0;">print</span><span style="color:#E1E4E8;">(_unameController.text)</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#6F42C1;">print</span><span style="color:#24292E;">(_unameController.text)</span></span></code></pre></div><h4 id="_3-监听文本变化" tabindex="-1">3）监听文本变化 <a class="header-anchor" href="#_3-监听文本变化" aria-label="Permalink to &quot;3）监听文本变化&quot;">​</a></h4><p>监听文本变化也有两种方式：</p><ol><li><p>设置<code>onChange</code>回调，如：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">    autofocus</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">true</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">    onChanged</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> (v) {</span></span>
<span class="line"><span style="color:#E1E4E8;">      </span><span style="color:#B392F0;">print</span><span style="color:#E1E4E8;">(</span><span style="color:#9ECBFF;">&quot;onChange: $</span><span style="color:#79B8FF;">v</span><span style="color:#9ECBFF;">&quot;</span><span style="color:#E1E4E8;">);</span></span>
<span class="line"><span style="color:#E1E4E8;">    }</span></span>
<span class="line"><span style="color:#E1E4E8;">)</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">    autofocus</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">true</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">    onChanged</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> (v) {</span></span>
<span class="line"><span style="color:#24292E;">      </span><span style="color:#6F42C1;">print</span><span style="color:#24292E;">(</span><span style="color:#032F62;">&quot;onChange: $</span><span style="color:#005CC5;">v</span><span style="color:#032F62;">&quot;</span><span style="color:#24292E;">);</span></span>
<span class="line"><span style="color:#24292E;">    }</span></span>
<span class="line"><span style="color:#24292E;">)</span></span></code></pre></div></li><li><p>通过<code>controller</code>监听，如：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#F97583;">@override</span></span>
<span class="line"><span style="color:#F97583;">void</span><span style="color:#E1E4E8;"> </span><span style="color:#B392F0;">initState</span><span style="color:#E1E4E8;">() {</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#6A737D;">//监听输入改变  </span></span>
<span class="line"><span style="color:#E1E4E8;">  _unameController.</span><span style="color:#B392F0;">addListener</span><span style="color:#E1E4E8;">((){</span></span>
<span class="line"><span style="color:#E1E4E8;">    </span><span style="color:#B392F0;">print</span><span style="color:#E1E4E8;">(_unameController.text);</span></span>
<span class="line"><span style="color:#E1E4E8;">  });</span></span>
<span class="line"><span style="color:#E1E4E8;">}</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#D73A49;">@override</span></span>
<span class="line"><span style="color:#D73A49;">void</span><span style="color:#24292E;"> </span><span style="color:#6F42C1;">initState</span><span style="color:#24292E;">() {</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#6A737D;">//监听输入改变  </span></span>
<span class="line"><span style="color:#24292E;">  _unameController.</span><span style="color:#6F42C1;">addListener</span><span style="color:#24292E;">((){</span></span>
<span class="line"><span style="color:#24292E;">    </span><span style="color:#6F42C1;">print</span><span style="color:#24292E;">(_unameController.text);</span></span>
<span class="line"><span style="color:#24292E;">  });</span></span>
<span class="line"><span style="color:#24292E;">}</span></span></code></pre></div></li></ol><p>两种方式相比，<code>onChanged</code>是专门用于监听文本变化，而<code>controller</code>的功能却多一些，除了能监听文本变化外，它还可以设置默认值、选择文本，下面我们看一个例子：</p><p>创建一个<code>controller</code>:</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;"> _selectionController </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;">();</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;"> _selectionController </span><span style="color:#D73A49;">=</span><span style="color:#24292E;">  </span><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;">();</span></span></code></pre></div><p>设置默认值，并从第三个字符开始选中后面的字符</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#E1E4E8;">_selectionController.text</span><span style="color:#F97583;">=</span><span style="color:#9ECBFF;">&quot;hello world!&quot;</span><span style="color:#E1E4E8;">;</span></span>
<span class="line"><span style="color:#E1E4E8;">_selectionController.selection</span><span style="color:#F97583;">=</span><span style="color:#79B8FF;">TextSelection</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">    baseOffset</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">2</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">    extentOffset</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> _selectionController.text.length</span></span>
<span class="line"><span style="color:#E1E4E8;">);</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#24292E;">_selectionController.text</span><span style="color:#D73A49;">=</span><span style="color:#032F62;">&quot;hello world!&quot;</span><span style="color:#24292E;">;</span></span>
<span class="line"><span style="color:#24292E;">_selectionController.selection</span><span style="color:#D73A49;">=</span><span style="color:#005CC5;">TextSelection</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">    baseOffset</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">2</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">    extentOffset</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> _selectionController.text.length</span></span>
<span class="line"><span style="color:#24292E;">);</span></span></code></pre></div><p>设置<code>controller</code>:</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">  controller</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> _selectionController,</span></span>
<span class="line"><span style="color:#E1E4E8;">)</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">  controller</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> _selectionController,</span></span>
<span class="line"><span style="color:#24292E;">)</span></span></code></pre></div><p>运行效果如图3-20所示：</p><p><img src="/assets/3-20.956eb230.png" alt="图3-20"></p><h4 id="_4-控制焦点" tabindex="-1">4）控制焦点 <a class="header-anchor" href="#_4-控制焦点" aria-label="Permalink to &quot;4）控制焦点&quot;">​</a></h4><p>焦点可以通过<code>FocusNode</code>和<code>FocusScopeNode</code>来控制，默认情况下，焦点由<code>FocusScope</code>来管理，它代表焦点控制范围，可以在这个范围内可以通过<code>FocusScopeNode</code>在输入框之间移动焦点、设置默认焦点等。我们可以通过<code>FocusScope.of(context)</code> 来获取Widget树中默认的<code>FocusScopeNode</code>。下面看一个示例，在此示例中创建两个<code>TextField</code>，第一个自动获取焦点，然后创建两个按钮：</p><ul><li>点击第一个按钮可以将焦点从第一个<code>TextField</code>挪到第二个<code>TextField</code>。</li><li>点击第二个按钮可以关闭键盘。</li></ul><p>我们要实现的效果如图3-21所示：</p><p><img src="/assets/3-21.b4864aa0.png" alt="图3-21"></p><p>代码如下：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#F97583;">class</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">FocusTestRoute</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">extends</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">StatefulWidget</span><span style="color:#E1E4E8;"> {</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#F97583;">@override</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">_FocusTestRouteState</span><span style="color:#E1E4E8;"> </span><span style="color:#B392F0;">createState</span><span style="color:#E1E4E8;">() </span><span style="color:#F97583;">=&gt;</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">_FocusTestRouteState</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F97583;">class</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">_FocusTestRouteState</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">extends</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">State</span><span style="color:#E1E4E8;">&lt;</span><span style="color:#79B8FF;">FocusTestRoute</span><span style="color:#E1E4E8;">&gt; {</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">FocusNode</span><span style="color:#E1E4E8;"> focusNode1 </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">FocusNode</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">FocusNode</span><span style="color:#E1E4E8;"> focusNode2 </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">FocusNode</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">FocusScopeNode</span><span style="color:#F97583;">?</span><span style="color:#E1E4E8;"> focusScopeNode;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#F97583;">@override</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">Widget</span><span style="color:#E1E4E8;"> </span><span style="color:#B392F0;">build</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">BuildContext</span><span style="color:#E1E4E8;"> context) {</span></span>
<span class="line"><span style="color:#E1E4E8;">    </span><span style="color:#F97583;">return</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Padding</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      padding</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">EdgeInsets</span><span style="color:#E1E4E8;">.</span><span style="color:#B392F0;">all</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">16.0</span><span style="color:#E1E4E8;">),</span></span>
<span class="line"><span style="color:#E1E4E8;">      child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Column</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">        children</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">&lt;</span><span style="color:#79B8FF;">Widget</span><span style="color:#F97583;">&gt;</span><span style="color:#E1E4E8;">[</span></span>
<span class="line"><span style="color:#E1E4E8;">          </span><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">            autofocus</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">true</span><span style="color:#E1E4E8;">, </span></span>
<span class="line"><span style="color:#E1E4E8;">            focusNode</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> focusNode1,</span><span style="color:#6A737D;">//关联focusNode1</span></span>
<span class="line"><span style="color:#E1E4E8;">            decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">                labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;input1&quot;</span></span>
<span class="line"><span style="color:#E1E4E8;">            ),</span></span>
<span class="line"><span style="color:#E1E4E8;">          ),</span></span>
<span class="line"><span style="color:#E1E4E8;">          </span><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">            focusNode</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> focusNode2,</span><span style="color:#6A737D;">//关联focusNode2</span></span>
<span class="line"><span style="color:#E1E4E8;">            decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">                labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;input2&quot;</span></span>
<span class="line"><span style="color:#E1E4E8;">            ),</span></span>
<span class="line"><span style="color:#E1E4E8;">          ),</span></span>
<span class="line"><span style="color:#E1E4E8;">          </span><span style="color:#79B8FF;">Builder</span><span style="color:#E1E4E8;">(builder</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> (ctx) {</span></span>
<span class="line"><span style="color:#E1E4E8;">            </span><span style="color:#F97583;">return</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Column</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">              children</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">&lt;</span><span style="color:#79B8FF;">Widget</span><span style="color:#F97583;">&gt;</span><span style="color:#E1E4E8;">[</span></span>
<span class="line"><span style="color:#E1E4E8;">                </span><span style="color:#79B8FF;">ElevatedButton</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">                  child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Text</span><span style="color:#E1E4E8;">(</span><span style="color:#9ECBFF;">&quot;移动焦点&quot;</span><span style="color:#E1E4E8;">),</span></span>
<span class="line"><span style="color:#E1E4E8;">                  onPressed</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> () {</span></span>
<span class="line"><span style="color:#E1E4E8;">                    </span><span style="color:#6A737D;">//将焦点从第一个TextField移到第二个TextField</span></span>
<span class="line"><span style="color:#E1E4E8;">                    </span><span style="color:#6A737D;">// 这是一种写法 FocusScope.of(context).requestFocus(focusNode2);</span></span>
<span class="line"><span style="color:#E1E4E8;">                    </span><span style="color:#6A737D;">// 这是第二种写法</span></span>
<span class="line"><span style="color:#E1E4E8;">                    </span><span style="color:#F97583;">if</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">null</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">==</span><span style="color:#E1E4E8;"> focusScopeNode){</span></span>
<span class="line"><span style="color:#E1E4E8;">                      focusScopeNode </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">FocusScope</span><span style="color:#E1E4E8;">.</span><span style="color:#B392F0;">of</span><span style="color:#E1E4E8;">(context);</span></span>
<span class="line"><span style="color:#E1E4E8;">                    }</span></span>
<span class="line"><span style="color:#E1E4E8;">                    focusScopeNode.</span><span style="color:#B392F0;">requestFocus</span><span style="color:#E1E4E8;">(focusNode2);</span></span>
<span class="line"><span style="color:#E1E4E8;">                  },</span></span>
<span class="line"><span style="color:#E1E4E8;">                ),</span></span>
<span class="line"><span style="color:#E1E4E8;">                </span><span style="color:#79B8FF;">ElevatedButton</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">                  child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Text</span><span style="color:#E1E4E8;">(</span><span style="color:#9ECBFF;">&quot;隐藏键盘&quot;</span><span style="color:#E1E4E8;">),</span></span>
<span class="line"><span style="color:#E1E4E8;">                  onPressed</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> () {</span></span>
<span class="line"><span style="color:#E1E4E8;">                    </span><span style="color:#6A737D;">// 当所有编辑框都失去焦点时键盘就会收起  </span></span>
<span class="line"><span style="color:#E1E4E8;">                    focusNode1.</span><span style="color:#B392F0;">unfocus</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">                    focusNode2.</span><span style="color:#B392F0;">unfocus</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">                  },</span></span>
<span class="line"><span style="color:#E1E4E8;">                ),</span></span>
<span class="line"><span style="color:#E1E4E8;">              ],</span></span>
<span class="line"><span style="color:#E1E4E8;">            );</span></span>
<span class="line"><span style="color:#E1E4E8;">          },</span></span>
<span class="line"><span style="color:#E1E4E8;">          ),</span></span>
<span class="line"><span style="color:#E1E4E8;">        ],</span></span>
<span class="line"><span style="color:#E1E4E8;">      ),</span></span>
<span class="line"><span style="color:#E1E4E8;">    );</span></span>
<span class="line"><span style="color:#E1E4E8;">  }</span></span>
<span class="line"></span>
<span class="line"><span style="color:#E1E4E8;">}</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#D73A49;">class</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">FocusTestRoute</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">extends</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">StatefulWidget</span><span style="color:#24292E;"> {</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#D73A49;">@override</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">_FocusTestRouteState</span><span style="color:#24292E;"> </span><span style="color:#6F42C1;">createState</span><span style="color:#24292E;">() </span><span style="color:#D73A49;">=&gt;</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">_FocusTestRouteState</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#D73A49;">class</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">_FocusTestRouteState</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">extends</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">State</span><span style="color:#24292E;">&lt;</span><span style="color:#005CC5;">FocusTestRoute</span><span style="color:#24292E;">&gt; {</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">FocusNode</span><span style="color:#24292E;"> focusNode1 </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">FocusNode</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">FocusNode</span><span style="color:#24292E;"> focusNode2 </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">FocusNode</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">FocusScopeNode</span><span style="color:#D73A49;">?</span><span style="color:#24292E;"> focusScopeNode;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#D73A49;">@override</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">Widget</span><span style="color:#24292E;"> </span><span style="color:#6F42C1;">build</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">BuildContext</span><span style="color:#24292E;"> context) {</span></span>
<span class="line"><span style="color:#24292E;">    </span><span style="color:#D73A49;">return</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Padding</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      padding</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">EdgeInsets</span><span style="color:#24292E;">.</span><span style="color:#6F42C1;">all</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">16.0</span><span style="color:#24292E;">),</span></span>
<span class="line"><span style="color:#24292E;">      child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Column</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">        children</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">&lt;</span><span style="color:#005CC5;">Widget</span><span style="color:#D73A49;">&gt;</span><span style="color:#24292E;">[</span></span>
<span class="line"><span style="color:#24292E;">          </span><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">            autofocus</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">true</span><span style="color:#24292E;">, </span></span>
<span class="line"><span style="color:#24292E;">            focusNode</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> focusNode1,</span><span style="color:#6A737D;">//关联focusNode1</span></span>
<span class="line"><span style="color:#24292E;">            decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">                labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;input1&quot;</span></span>
<span class="line"><span style="color:#24292E;">            ),</span></span>
<span class="line"><span style="color:#24292E;">          ),</span></span>
<span class="line"><span style="color:#24292E;">          </span><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">            focusNode</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> focusNode2,</span><span style="color:#6A737D;">//关联focusNode2</span></span>
<span class="line"><span style="color:#24292E;">            decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">                labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;input2&quot;</span></span>
<span class="line"><span style="color:#24292E;">            ),</span></span>
<span class="line"><span style="color:#24292E;">          ),</span></span>
<span class="line"><span style="color:#24292E;">          </span><span style="color:#005CC5;">Builder</span><span style="color:#24292E;">(builder</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> (ctx) {</span></span>
<span class="line"><span style="color:#24292E;">            </span><span style="color:#D73A49;">return</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Column</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">              children</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">&lt;</span><span style="color:#005CC5;">Widget</span><span style="color:#D73A49;">&gt;</span><span style="color:#24292E;">[</span></span>
<span class="line"><span style="color:#24292E;">                </span><span style="color:#005CC5;">ElevatedButton</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">                  child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Text</span><span style="color:#24292E;">(</span><span style="color:#032F62;">&quot;移动焦点&quot;</span><span style="color:#24292E;">),</span></span>
<span class="line"><span style="color:#24292E;">                  onPressed</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> () {</span></span>
<span class="line"><span style="color:#24292E;">                    </span><span style="color:#6A737D;">//将焦点从第一个TextField移到第二个TextField</span></span>
<span class="line"><span style="color:#24292E;">                    </span><span style="color:#6A737D;">// 这是一种写法 FocusScope.of(context).requestFocus(focusNode2);</span></span>
<span class="line"><span style="color:#24292E;">                    </span><span style="color:#6A737D;">// 这是第二种写法</span></span>
<span class="line"><span style="color:#24292E;">                    </span><span style="color:#D73A49;">if</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">null</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">==</span><span style="color:#24292E;"> focusScopeNode){</span></span>
<span class="line"><span style="color:#24292E;">                      focusScopeNode </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">FocusScope</span><span style="color:#24292E;">.</span><span style="color:#6F42C1;">of</span><span style="color:#24292E;">(context);</span></span>
<span class="line"><span style="color:#24292E;">                    }</span></span>
<span class="line"><span style="color:#24292E;">                    focusScopeNode.</span><span style="color:#6F42C1;">requestFocus</span><span style="color:#24292E;">(focusNode2);</span></span>
<span class="line"><span style="color:#24292E;">                  },</span></span>
<span class="line"><span style="color:#24292E;">                ),</span></span>
<span class="line"><span style="color:#24292E;">                </span><span style="color:#005CC5;">ElevatedButton</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">                  child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Text</span><span style="color:#24292E;">(</span><span style="color:#032F62;">&quot;隐藏键盘&quot;</span><span style="color:#24292E;">),</span></span>
<span class="line"><span style="color:#24292E;">                  onPressed</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> () {</span></span>
<span class="line"><span style="color:#24292E;">                    </span><span style="color:#6A737D;">// 当所有编辑框都失去焦点时键盘就会收起  </span></span>
<span class="line"><span style="color:#24292E;">                    focusNode1.</span><span style="color:#6F42C1;">unfocus</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">                    focusNode2.</span><span style="color:#6F42C1;">unfocus</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">                  },</span></span>
<span class="line"><span style="color:#24292E;">                ),</span></span>
<span class="line"><span style="color:#24292E;">              ],</span></span>
<span class="line"><span style="color:#24292E;">            );</span></span>
<span class="line"><span style="color:#24292E;">          },</span></span>
<span class="line"><span style="color:#24292E;">          ),</span></span>
<span class="line"><span style="color:#24292E;">        ],</span></span>
<span class="line"><span style="color:#24292E;">      ),</span></span>
<span class="line"><span style="color:#24292E;">    );</span></span>
<span class="line"><span style="color:#24292E;">  }</span></span>
<span class="line"></span>
<span class="line"><span style="color:#24292E;">}</span></span></code></pre></div><p><code>FocusNode</code>和<code>FocusScopeNode</code>还有一些其他的方法，详情可以查看API文档。</p><h4 id="_5-监听焦点状态改变事件" tabindex="-1">5）监听焦点状态改变事件 <a class="header-anchor" href="#_5-监听焦点状态改变事件" aria-label="Permalink to &quot;5）监听焦点状态改变事件&quot;">​</a></h4><p><code>FocusNode</code>继承自<code>ChangeNotifier</code>，通过<code>FocusNode</code>可以监听焦点的改变事件，如：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#E1E4E8;">...</span></span>
<span class="line"><span style="color:#6A737D;">// 创建 focusNode   </span></span>
<span class="line"><span style="color:#79B8FF;">FocusNode</span><span style="color:#E1E4E8;"> focusNode </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">FocusNode</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">...</span></span>
<span class="line"><span style="color:#6A737D;">// focusNode绑定输入框   </span></span>
<span class="line"><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(focusNode</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> focusNode);</span></span>
<span class="line"><span style="color:#E1E4E8;">...</span></span>
<span class="line"><span style="color:#6A737D;">// 监听焦点变化    </span></span>
<span class="line"><span style="color:#E1E4E8;">focusNode.</span><span style="color:#B392F0;">addListener</span><span style="color:#E1E4E8;">((){</span></span>
<span class="line"><span style="color:#E1E4E8;">   </span><span style="color:#B392F0;">print</span><span style="color:#E1E4E8;">(focusNode.hasFocus);</span></span>
<span class="line"><span style="color:#E1E4E8;">});</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#24292E;">...</span></span>
<span class="line"><span style="color:#6A737D;">// 创建 focusNode   </span></span>
<span class="line"><span style="color:#005CC5;">FocusNode</span><span style="color:#24292E;"> focusNode </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">FocusNode</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">...</span></span>
<span class="line"><span style="color:#6A737D;">// focusNode绑定输入框   </span></span>
<span class="line"><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(focusNode</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> focusNode);</span></span>
<span class="line"><span style="color:#24292E;">...</span></span>
<span class="line"><span style="color:#6A737D;">// 监听焦点变化    </span></span>
<span class="line"><span style="color:#24292E;">focusNode.</span><span style="color:#6F42C1;">addListener</span><span style="color:#24292E;">((){</span></span>
<span class="line"><span style="color:#24292E;">   </span><span style="color:#6F42C1;">print</span><span style="color:#24292E;">(focusNode.hasFocus);</span></span>
<span class="line"><span style="color:#24292E;">});</span></span></code></pre></div><p>获得焦点时<code>focusNode.hasFocus</code>值为<code>true</code>，失去焦点时为<code>false</code>。</p><h4 id="_6-自定义样式" tabindex="-1">6）自定义样式 <a class="header-anchor" href="#_6-自定义样式" aria-label="Permalink to &quot;6）自定义样式&quot;">​</a></h4><p>虽然我们可以通过<code>decoration</code>属性来定义输入框样式，下面以自定义输入框下划线颜色为例来介绍一下：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">  decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">    labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;请输入用户名&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">    prefixIcon</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Icon</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Icons</span><span style="color:#E1E4E8;">.person),</span></span>
<span class="line"><span style="color:#E1E4E8;">    </span><span style="color:#6A737D;">// 未获得焦点下划线设为灰色</span></span>
<span class="line"><span style="color:#E1E4E8;">    enabledBorder</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">UnderlineInputBorder</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      borderSide</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">BorderSide</span><span style="color:#E1E4E8;">(color</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Colors</span><span style="color:#E1E4E8;">.grey),</span></span>
<span class="line"><span style="color:#E1E4E8;">    ),</span></span>
<span class="line"><span style="color:#E1E4E8;">    </span><span style="color:#6A737D;">//获得焦点下划线设为蓝色</span></span>
<span class="line"><span style="color:#E1E4E8;">    focusedBorder</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">UnderlineInputBorder</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      borderSide</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">BorderSide</span><span style="color:#E1E4E8;">(color</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Colors</span><span style="color:#E1E4E8;">.blue),</span></span>
<span class="line"><span style="color:#E1E4E8;">    ),</span></span>
<span class="line"><span style="color:#E1E4E8;">  ),</span></span>
<span class="line"><span style="color:#E1E4E8;">),</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">  decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">    labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;请输入用户名&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">    prefixIcon</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Icon</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Icons</span><span style="color:#24292E;">.person),</span></span>
<span class="line"><span style="color:#24292E;">    </span><span style="color:#6A737D;">// 未获得焦点下划线设为灰色</span></span>
<span class="line"><span style="color:#24292E;">    enabledBorder</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">UnderlineInputBorder</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      borderSide</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">BorderSide</span><span style="color:#24292E;">(color</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Colors</span><span style="color:#24292E;">.grey),</span></span>
<span class="line"><span style="color:#24292E;">    ),</span></span>
<span class="line"><span style="color:#24292E;">    </span><span style="color:#6A737D;">//获得焦点下划线设为蓝色</span></span>
<span class="line"><span style="color:#24292E;">    focusedBorder</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">UnderlineInputBorder</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      borderSide</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">BorderSide</span><span style="color:#24292E;">(color</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Colors</span><span style="color:#24292E;">.blue),</span></span>
<span class="line"><span style="color:#24292E;">    ),</span></span>
<span class="line"><span style="color:#24292E;">  ),</span></span>
<span class="line"><span style="color:#24292E;">),</span></span></code></pre></div><p>上面代码我们直接通过InputDecoration的enabledBorder和focusedBorder来分别设置了输入框在未获取焦点和获得焦点后的下划线颜色。另外，我们也可以通过主题来自定义输入框的样式，下面我们探索一下如何在不使用enabledBorder和focusedBorder的情况下来自定义下滑线颜色。</p><p>由于<code>TextField</code>在绘制下划线时使用的颜色是主题色里面的<code>hintColor</code>，但提示文本颜色也是用的<code>hintColor</code>， 如果我们直接修改<code>hintColor</code>，那么下划线和提示文本的颜色都会变。值得高兴的是<code>decoration</code>中可以设置<code>hintStyle</code>，它可以覆盖<code>hintColor</code>，并且主题中可以通过<code>inputDecorationTheme</code>来设置输入框默认的<code>decoration</code>。所以我们可以通过主题来自定义，代码如下：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">Theme</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">  data</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Theme</span><span style="color:#E1E4E8;">.</span><span style="color:#B392F0;">of</span><span style="color:#E1E4E8;">(context).</span><span style="color:#B392F0;">copyWith</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      hintColor</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Colors</span><span style="color:#E1E4E8;">.grey[</span><span style="color:#79B8FF;">200</span><span style="color:#E1E4E8;">], </span><span style="color:#6A737D;">//定义下划线颜色</span></span>
<span class="line"><span style="color:#E1E4E8;">      inputDecorationTheme</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecorationTheme</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">          labelStyle</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextStyle</span><span style="color:#E1E4E8;">(color</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Colors</span><span style="color:#E1E4E8;">.grey),</span><span style="color:#6A737D;">//定义label字体样式</span></span>
<span class="line"><span style="color:#E1E4E8;">          hintStyle</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextStyle</span><span style="color:#E1E4E8;">(color</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Colors</span><span style="color:#E1E4E8;">.grey, fontSize</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">14.0</span><span style="color:#E1E4E8;">)</span><span style="color:#6A737D;">//定义提示文本样式</span></span>
<span class="line"><span style="color:#E1E4E8;">      )</span></span>
<span class="line"><span style="color:#E1E4E8;">  ),</span></span>
<span class="line"><span style="color:#E1E4E8;">  child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Column</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">    children</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">&lt;</span><span style="color:#79B8FF;">Widget</span><span style="color:#F97583;">&gt;</span><span style="color:#E1E4E8;">[</span></span>
<span class="line"><span style="color:#E1E4E8;">      </span><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">        decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">            labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;用户名&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">            hintText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;用户名或邮箱&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">            prefixIcon</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Icon</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Icons</span><span style="color:#E1E4E8;">.person)</span></span>
<span class="line"><span style="color:#E1E4E8;">        ),</span></span>
<span class="line"><span style="color:#E1E4E8;">      ),</span></span>
<span class="line"><span style="color:#E1E4E8;">      </span><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">        decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">            prefixIcon</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Icon</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Icons</span><span style="color:#E1E4E8;">.lock),</span></span>
<span class="line"><span style="color:#E1E4E8;">            labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;密码&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">            hintText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;您的登录密码&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">            hintStyle</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextStyle</span><span style="color:#E1E4E8;">(color</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Colors</span><span style="color:#E1E4E8;">.grey, fontSize</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">13.0</span><span style="color:#E1E4E8;">)</span></span>
<span class="line"><span style="color:#E1E4E8;">        ),</span></span>
<span class="line"><span style="color:#E1E4E8;">        obscureText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">true</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">      )</span></span>
<span class="line"><span style="color:#E1E4E8;">    ],</span></span>
<span class="line"><span style="color:#E1E4E8;">  )</span></span>
<span class="line"><span style="color:#E1E4E8;">)</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">Theme</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">  data</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Theme</span><span style="color:#24292E;">.</span><span style="color:#6F42C1;">of</span><span style="color:#24292E;">(context).</span><span style="color:#6F42C1;">copyWith</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      hintColor</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Colors</span><span style="color:#24292E;">.grey[</span><span style="color:#005CC5;">200</span><span style="color:#24292E;">], </span><span style="color:#6A737D;">//定义下划线颜色</span></span>
<span class="line"><span style="color:#24292E;">      inputDecorationTheme</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecorationTheme</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">          labelStyle</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextStyle</span><span style="color:#24292E;">(color</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Colors</span><span style="color:#24292E;">.grey),</span><span style="color:#6A737D;">//定义label字体样式</span></span>
<span class="line"><span style="color:#24292E;">          hintStyle</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextStyle</span><span style="color:#24292E;">(color</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Colors</span><span style="color:#24292E;">.grey, fontSize</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">14.0</span><span style="color:#24292E;">)</span><span style="color:#6A737D;">//定义提示文本样式</span></span>
<span class="line"><span style="color:#24292E;">      )</span></span>
<span class="line"><span style="color:#24292E;">  ),</span></span>
<span class="line"><span style="color:#24292E;">  child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Column</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">    children</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">&lt;</span><span style="color:#005CC5;">Widget</span><span style="color:#D73A49;">&gt;</span><span style="color:#24292E;">[</span></span>
<span class="line"><span style="color:#24292E;">      </span><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">        decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">            labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;用户名&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">            hintText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;用户名或邮箱&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">            prefixIcon</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Icon</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Icons</span><span style="color:#24292E;">.person)</span></span>
<span class="line"><span style="color:#24292E;">        ),</span></span>
<span class="line"><span style="color:#24292E;">      ),</span></span>
<span class="line"><span style="color:#24292E;">      </span><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">        decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">            prefixIcon</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Icon</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Icons</span><span style="color:#24292E;">.lock),</span></span>
<span class="line"><span style="color:#24292E;">            labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;密码&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">            hintText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;您的登录密码&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">            hintStyle</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextStyle</span><span style="color:#24292E;">(color</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Colors</span><span style="color:#24292E;">.grey, fontSize</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">13.0</span><span style="color:#24292E;">)</span></span>
<span class="line"><span style="color:#24292E;">        ),</span></span>
<span class="line"><span style="color:#24292E;">        obscureText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">true</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">      )</span></span>
<span class="line"><span style="color:#24292E;">    ],</span></span>
<span class="line"><span style="color:#24292E;">  )</span></span>
<span class="line"><span style="color:#24292E;">)</span></span></code></pre></div><p>运行效果如图3-22所示：</p><p><img src="/assets/3-22.0059ad13.png" alt="图3-22"></p><p>我们成功的自定义了下划线颜色和提问文字样式，细心的读者可能已经发现，通过这种方式自定义后，输入框在获取焦点时，<code>labelText</code>不会高亮显示了，正如上图中的&quot;用户名&quot;本应该显示蓝色，但现在却显示为灰色，并且我们还是无法定义下划线宽度。另一种灵活的方式是直接隐藏掉<code>TextField</code>本身的下划线，然后通过<code>Container</code>去嵌套定义样式，如:</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">Container</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">  child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">    keyboardType</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextInputType</span><span style="color:#E1E4E8;">.emailAddress,</span></span>
<span class="line"><span style="color:#E1E4E8;">    decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">        labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;Email&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">        hintText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;电子邮件地址&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">        prefixIcon</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Icon</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Icons</span><span style="color:#E1E4E8;">.email),</span></span>
<span class="line"><span style="color:#E1E4E8;">        border</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputBorder</span><span style="color:#E1E4E8;">.none </span><span style="color:#6A737D;">//隐藏下划线</span></span>
<span class="line"><span style="color:#E1E4E8;">    )</span></span>
<span class="line"><span style="color:#E1E4E8;">  ),</span></span>
<span class="line"><span style="color:#E1E4E8;">  decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">BoxDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      </span><span style="color:#6A737D;">// 下滑线浅灰色，宽度1像素</span></span>
<span class="line"><span style="color:#E1E4E8;">      border</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Border</span><span style="color:#E1E4E8;">(bottom</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">BorderSide</span><span style="color:#E1E4E8;">(color</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Colors</span><span style="color:#E1E4E8;">.grey[</span><span style="color:#79B8FF;">200</span><span style="color:#E1E4E8;">], width</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">1.0</span><span style="color:#E1E4E8;">))</span></span>
<span class="line"><span style="color:#E1E4E8;">  ),</span></span>
<span class="line"><span style="color:#E1E4E8;">)</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">Container</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">  child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">    keyboardType</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextInputType</span><span style="color:#24292E;">.emailAddress,</span></span>
<span class="line"><span style="color:#24292E;">    decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">        labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;Email&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">        hintText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;电子邮件地址&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">        prefixIcon</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Icon</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Icons</span><span style="color:#24292E;">.email),</span></span>
<span class="line"><span style="color:#24292E;">        border</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputBorder</span><span style="color:#24292E;">.none </span><span style="color:#6A737D;">//隐藏下划线</span></span>
<span class="line"><span style="color:#24292E;">    )</span></span>
<span class="line"><span style="color:#24292E;">  ),</span></span>
<span class="line"><span style="color:#24292E;">  decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">BoxDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      </span><span style="color:#6A737D;">// 下滑线浅灰色，宽度1像素</span></span>
<span class="line"><span style="color:#24292E;">      border</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Border</span><span style="color:#24292E;">(bottom</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">BorderSide</span><span style="color:#24292E;">(color</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Colors</span><span style="color:#24292E;">.grey[</span><span style="color:#005CC5;">200</span><span style="color:#24292E;">], width</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">1.0</span><span style="color:#24292E;">))</span></span>
<span class="line"><span style="color:#24292E;">  ),</span></span>
<span class="line"><span style="color:#24292E;">)</span></span></code></pre></div><p>运行效果如图3-23：</p><p><img src="/assets/3-23.4d9c310f.png" alt="3-23"></p><p>通过这种组件组合的方式，也可以定义背景圆角等。一般来说，优先通过<code>decoration</code>来自定义样式，如果<code>decoration</code>实现不了，再用widget组合的方式。</p><blockquote><p>思考题：在这个示例中，下划线颜色是固定的，所以获得焦点后颜色仍然为灰色，如何实现点击后下滑线也变色呢？</p></blockquote><h2 id="_3-5-2-表单form" tabindex="-1">3.5.2 表单Form <a class="header-anchor" href="#_3-5-2-表单form" aria-label="Permalink to &quot;3.5.2 表单Form&quot;">​</a></h2><p>实际业务中，在正式向服务器提交数据前，都会对各个输入框数据进行合法性校验，但是对每一个<code>TextField</code>都分别进行校验将会是一件很麻烦的事。还有，如果用户想清除一组<code>TextField</code>的内容，除了一个一个清除有没有什么更好的办法呢？为此，Flutter提供了一个<code>Form</code> 组件，它可以对输入框进行分组，然后进行一些统一操作，如输入内容校验、输入框重置以及输入内容保存。</p><h3 id="_1-form" tabindex="-1">1. Form <a class="header-anchor" href="#_1-form" aria-label="Permalink to &quot;1. Form&quot;">​</a></h3><p><code>Form</code>继承自<code>StatefulWidget</code>对象，它对应的状态类为<code>FormState</code>。我们先看看<code>Form</code>类的定义：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">Form</span><span style="color:#E1E4E8;">({</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#F97583;">required</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Widget</span><span style="color:#E1E4E8;"> child,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">bool</span><span style="color:#E1E4E8;"> autovalidate </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">false</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">WillPopCallback</span><span style="color:#E1E4E8;"> onWillPop,</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">VoidCallback</span><span style="color:#E1E4E8;"> onChanged,</span></span>
<span class="line"><span style="color:#E1E4E8;">})</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">Form</span><span style="color:#24292E;">({</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#D73A49;">required</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Widget</span><span style="color:#24292E;"> child,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">bool</span><span style="color:#24292E;"> autovalidate </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">false</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">WillPopCallback</span><span style="color:#24292E;"> onWillPop,</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">VoidCallback</span><span style="color:#24292E;"> onChanged,</span></span>
<span class="line"><span style="color:#24292E;">})</span></span></code></pre></div><ul><li><code>autovalidate</code>：是否自动校验输入内容；当为<code>true</code>时，每一个子 FormField 内容发生变化时都会自动校验合法性，并直接显示错误信息。否则，需要通过调用<code>FormState.validate()</code>来手动校验。</li><li><code>onWillPop</code>：决定<code>Form</code>所在的路由是否可以直接返回（如点击返回按钮），该回调返回一个<code>Future</code>对象，如果 Future 的最终结果是<code>false</code>，则当前路由不会返回；如果为<code>true</code>，则会返回到上一个路由。此属性通常用于拦截返回按钮。</li><li><code>onChanged</code>：<code>Form</code>的任意一个子<code>FormField</code>内容发生变化时会触发此回调。</li></ul><h3 id="_2-formfield" tabindex="-1">2. FormField <a class="header-anchor" href="#_2-formfield" aria-label="Permalink to &quot;2. FormField&quot;">​</a></h3><p><code>Form</code>的子孙元素必须是<code>FormField</code>类型，<code>FormField</code>是一个抽象类，定义几个属性，<code>FormState</code>内部通过它们来完成操作，<code>FormField</code>部分定义如下：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#F97583;">const</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">FormField</span><span style="color:#E1E4E8;">({</span></span>
<span class="line"><span style="color:#E1E4E8;">  ...</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">FormFieldSetter</span><span style="color:#E1E4E8;">&lt;</span><span style="color:#79B8FF;">T</span><span style="color:#E1E4E8;">&gt; onSaved, </span><span style="color:#6A737D;">//保存回调</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">FormFieldValidator</span><span style="color:#E1E4E8;">&lt;</span><span style="color:#79B8FF;">T</span><span style="color:#E1E4E8;">&gt;  validator, </span><span style="color:#6A737D;">//验证回调</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">T</span><span style="color:#E1E4E8;"> initialValue, </span><span style="color:#6A737D;">//初始值</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">bool</span><span style="color:#E1E4E8;"> autovalidate </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">false</span><span style="color:#E1E4E8;">, </span><span style="color:#6A737D;">//是否自动校验。</span></span>
<span class="line"><span style="color:#E1E4E8;">})</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#D73A49;">const</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">FormField</span><span style="color:#24292E;">({</span></span>
<span class="line"><span style="color:#24292E;">  ...</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">FormFieldSetter</span><span style="color:#24292E;">&lt;</span><span style="color:#005CC5;">T</span><span style="color:#24292E;">&gt; onSaved, </span><span style="color:#6A737D;">//保存回调</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">FormFieldValidator</span><span style="color:#24292E;">&lt;</span><span style="color:#005CC5;">T</span><span style="color:#24292E;">&gt;  validator, </span><span style="color:#6A737D;">//验证回调</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">T</span><span style="color:#24292E;"> initialValue, </span><span style="color:#6A737D;">//初始值</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">bool</span><span style="color:#24292E;"> autovalidate </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">false</span><span style="color:#24292E;">, </span><span style="color:#6A737D;">//是否自动校验。</span></span>
<span class="line"><span style="color:#24292E;">})</span></span></code></pre></div><p>为了方便使用，Flutter 提供了一个<code>TextFormField</code>组件，它继承自<code>FormField</code>类，也是<code>TextField</code>的一个包装类，所以除了<code>FormField</code>定义的属性之外，它还包括<code>TextField</code>的属性。</p><h3 id="_3-formstate" tabindex="-1">3. FormState <a class="header-anchor" href="#_3-formstate" aria-label="Permalink to &quot;3. FormState&quot;">​</a></h3><p><code>FormState</code>为<code>Form</code>的<code>State</code>类，可以通过<code>Form.of()</code>或<code>GlobalKey</code>获得。我们可以通过它来对<code>Form</code>的子孙<code>FormField</code>进行统一操作。我们看看其常用的三个方法：</p><ul><li><code>FormState.validate()</code>：调用此方法后，会调用<code>Form</code>子孙<code>FormField的validate</code>回调，如果有一个校验失败，则返回false，所有校验失败项都会返回用户返回的错误提示。</li><li><code>FormState.save()</code>：调用此方法后，会调用<code>Form</code>子孙<code>FormField</code>的<code>save</code>回调，用于保存表单内容</li><li><code>FormState.reset()</code>：调用此方法后，会将子孙<code>FormField</code>的内容清空。</li></ul><h3 id="_4-示例" tabindex="-1">4. 示例 <a class="header-anchor" href="#_4-示例" aria-label="Permalink to &quot;4. 示例&quot;">​</a></h3><p>我们修改一下上面用户登录的示例，在提交之前校验：</p><ol><li>用户名不能为空，如果为空则提示“用户名不能为空”。</li><li>密码不能少于 6 位，如果小于 6 为则提示“密码不能少于 6 位”。</li></ol><p>完整代码：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#F97583;">import</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&#39;package:flutter/material.dart&#39;</span><span style="color:#E1E4E8;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F97583;">class</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">FormTestRoute</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">extends</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">StatefulWidget</span><span style="color:#E1E4E8;"> {</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#F97583;">@override</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">_FormTestRouteState</span><span style="color:#E1E4E8;"> </span><span style="color:#B392F0;">createState</span><span style="color:#E1E4E8;">() </span><span style="color:#F97583;">=&gt;</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">_FormTestRouteState</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#F97583;">class</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">_FormTestRouteState</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">extends</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">State</span><span style="color:#E1E4E8;">&lt;</span><span style="color:#79B8FF;">FormTestRoute</span><span style="color:#E1E4E8;">&gt; {</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;"> _unameController </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;"> _pwdController </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">TextEditingController</span><span style="color:#E1E4E8;">();</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">GlobalKey</span><span style="color:#E1E4E8;"> _formKey </span><span style="color:#F97583;">=</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">GlobalKey</span><span style="color:#E1E4E8;">&lt;</span><span style="color:#79B8FF;">FormState</span><span style="color:#E1E4E8;">&gt;();</span></span>
<span class="line"></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#F97583;">@override</span></span>
<span class="line"><span style="color:#E1E4E8;">  </span><span style="color:#79B8FF;">Widget</span><span style="color:#E1E4E8;"> </span><span style="color:#B392F0;">build</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">BuildContext</span><span style="color:#E1E4E8;"> context) {</span></span>
<span class="line"><span style="color:#E1E4E8;">    </span><span style="color:#F97583;">return</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Form</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      key</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> _formKey, </span><span style="color:#6A737D;">//设置globalKey，用于后面获取FormState</span></span>
<span class="line"><span style="color:#E1E4E8;">      autovalidateMode</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">AutovalidateMode</span><span style="color:#E1E4E8;">.onUserInteraction,</span></span>
<span class="line"><span style="color:#E1E4E8;">      child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Column</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">        children</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">&lt;</span><span style="color:#79B8FF;">Widget</span><span style="color:#F97583;">&gt;</span><span style="color:#E1E4E8;">[</span></span>
<span class="line"><span style="color:#E1E4E8;">          </span><span style="color:#79B8FF;">TextFormField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">            autofocus</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">true</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">            controller</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> _unameController,</span></span>
<span class="line"><span style="color:#E1E4E8;">            decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">              labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;用户名&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">              hintText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;用户名或邮箱&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">              icon</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Icon</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Icons</span><span style="color:#E1E4E8;">.person),</span></span>
<span class="line"><span style="color:#E1E4E8;">            ),</span></span>
<span class="line"><span style="color:#E1E4E8;">            </span><span style="color:#6A737D;">// 校验用户名</span></span>
<span class="line"><span style="color:#E1E4E8;">            validator</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> (v) {</span></span>
<span class="line"><span style="color:#E1E4E8;">              </span><span style="color:#F97583;">return</span><span style="color:#E1E4E8;"> v</span><span style="color:#F97583;">!</span><span style="color:#E1E4E8;">.</span><span style="color:#B392F0;">trim</span><span style="color:#E1E4E8;">().isNotEmpty </span><span style="color:#F97583;">?</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">null</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;用户名不能为空&quot;</span><span style="color:#E1E4E8;">;</span></span>
<span class="line"><span style="color:#E1E4E8;">            },</span></span>
<span class="line"><span style="color:#E1E4E8;">          ),</span></span>
<span class="line"><span style="color:#E1E4E8;">          </span><span style="color:#79B8FF;">TextFormField</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">            controller</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> _pwdController,</span></span>
<span class="line"><span style="color:#E1E4E8;">            decoration</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">InputDecoration</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">              labelText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;密码&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">              hintText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;您的登录密码&quot;</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">              icon</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Icon</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Icons</span><span style="color:#E1E4E8;">.lock),</span></span>
<span class="line"><span style="color:#E1E4E8;">            ),</span></span>
<span class="line"><span style="color:#E1E4E8;">            obscureText</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">true</span><span style="color:#E1E4E8;">,</span></span>
<span class="line"><span style="color:#E1E4E8;">            </span><span style="color:#6A737D;">//校验密码</span></span>
<span class="line"><span style="color:#E1E4E8;">            validator</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> (v) {</span></span>
<span class="line"><span style="color:#E1E4E8;">              </span><span style="color:#F97583;">return</span><span style="color:#E1E4E8;"> v</span><span style="color:#F97583;">!</span><span style="color:#E1E4E8;">.</span><span style="color:#B392F0;">trim</span><span style="color:#E1E4E8;">().length </span><span style="color:#F97583;">&gt;</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">5</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">?</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">null</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#9ECBFF;">&quot;密码不能少于6位&quot;</span><span style="color:#E1E4E8;">;</span></span>
<span class="line"><span style="color:#E1E4E8;">            },</span></span>
<span class="line"><span style="color:#E1E4E8;">          ),</span></span>
<span class="line"><span style="color:#E1E4E8;">          </span><span style="color:#6A737D;">// 登录按钮</span></span>
<span class="line"><span style="color:#E1E4E8;">          </span><span style="color:#79B8FF;">Padding</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">            padding</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">const</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">EdgeInsets</span><span style="color:#E1E4E8;">.</span><span style="color:#B392F0;">only</span><span style="color:#E1E4E8;">(top</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">28.0</span><span style="color:#E1E4E8;">),</span></span>
<span class="line"><span style="color:#E1E4E8;">            child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Row</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">              children</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">&lt;</span><span style="color:#79B8FF;">Widget</span><span style="color:#F97583;">&gt;</span><span style="color:#E1E4E8;">[</span></span>
<span class="line"><span style="color:#E1E4E8;">                </span><span style="color:#79B8FF;">Expanded</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">                  child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">ElevatedButton</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">                    child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Padding</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">                      padding</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#F97583;">const</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">EdgeInsets</span><span style="color:#E1E4E8;">.</span><span style="color:#B392F0;">all</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">16.0</span><span style="color:#E1E4E8;">),</span></span>
<span class="line"><span style="color:#E1E4E8;">                      child</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">Text</span><span style="color:#E1E4E8;">(</span><span style="color:#9ECBFF;">&quot;登录&quot;</span><span style="color:#E1E4E8;">),</span></span>
<span class="line"><span style="color:#E1E4E8;">                    ),</span></span>
<span class="line"><span style="color:#E1E4E8;">                    onPressed</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> () {</span></span>
<span class="line"><span style="color:#E1E4E8;">                      </span><span style="color:#6A737D;">// 通过_formKey.currentState 获取FormState后，</span></span>
<span class="line"><span style="color:#E1E4E8;">                      </span><span style="color:#6A737D;">// 调用validate()方法校验用户名密码是否合法，校验</span></span>
<span class="line"><span style="color:#E1E4E8;">                      </span><span style="color:#6A737D;">// 通过后再提交数据。</span></span>
<span class="line"><span style="color:#E1E4E8;">                      </span><span style="color:#F97583;">if</span><span style="color:#E1E4E8;"> ((_formKey.currentState </span><span style="color:#F97583;">as</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">FormState</span><span style="color:#E1E4E8;">).</span><span style="color:#B392F0;">validate</span><span style="color:#E1E4E8;">()) {</span></span>
<span class="line"><span style="color:#E1E4E8;">                        </span><span style="color:#6A737D;">//验证通过提交数据</span></span>
<span class="line"><span style="color:#E1E4E8;">                      }</span></span>
<span class="line"><span style="color:#E1E4E8;">                    },</span></span>
<span class="line"><span style="color:#E1E4E8;">                  ),</span></span>
<span class="line"><span style="color:#E1E4E8;">                ),</span></span>
<span class="line"><span style="color:#E1E4E8;">              ],</span></span>
<span class="line"><span style="color:#E1E4E8;">            ),</span></span>
<span class="line"><span style="color:#E1E4E8;">          )</span></span>
<span class="line"><span style="color:#E1E4E8;">        ],</span></span>
<span class="line"><span style="color:#E1E4E8;">      ),</span></span>
<span class="line"><span style="color:#E1E4E8;">    );</span></span>
<span class="line"><span style="color:#E1E4E8;">  }</span></span>
<span class="line"><span style="color:#E1E4E8;">}</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#D73A49;">import</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&#39;package:flutter/material.dart&#39;</span><span style="color:#24292E;">;</span></span>
<span class="line"></span>
<span class="line"><span style="color:#D73A49;">class</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">FormTestRoute</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">extends</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">StatefulWidget</span><span style="color:#24292E;"> {</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#D73A49;">@override</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">_FormTestRouteState</span><span style="color:#24292E;"> </span><span style="color:#6F42C1;">createState</span><span style="color:#24292E;">() </span><span style="color:#D73A49;">=&gt;</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">_FormTestRouteState</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">}</span></span>
<span class="line"></span>
<span class="line"><span style="color:#D73A49;">class</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">_FormTestRouteState</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">extends</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">State</span><span style="color:#24292E;">&lt;</span><span style="color:#005CC5;">FormTestRoute</span><span style="color:#24292E;">&gt; {</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;"> _unameController </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;"> _pwdController </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">TextEditingController</span><span style="color:#24292E;">();</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">GlobalKey</span><span style="color:#24292E;"> _formKey </span><span style="color:#D73A49;">=</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">GlobalKey</span><span style="color:#24292E;">&lt;</span><span style="color:#005CC5;">FormState</span><span style="color:#24292E;">&gt;();</span></span>
<span class="line"></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#D73A49;">@override</span></span>
<span class="line"><span style="color:#24292E;">  </span><span style="color:#005CC5;">Widget</span><span style="color:#24292E;"> </span><span style="color:#6F42C1;">build</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">BuildContext</span><span style="color:#24292E;"> context) {</span></span>
<span class="line"><span style="color:#24292E;">    </span><span style="color:#D73A49;">return</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Form</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      key</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> _formKey, </span><span style="color:#6A737D;">//设置globalKey，用于后面获取FormState</span></span>
<span class="line"><span style="color:#24292E;">      autovalidateMode</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">AutovalidateMode</span><span style="color:#24292E;">.onUserInteraction,</span></span>
<span class="line"><span style="color:#24292E;">      child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Column</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">        children</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">&lt;</span><span style="color:#005CC5;">Widget</span><span style="color:#D73A49;">&gt;</span><span style="color:#24292E;">[</span></span>
<span class="line"><span style="color:#24292E;">          </span><span style="color:#005CC5;">TextFormField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">            autofocus</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">true</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">            controller</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> _unameController,</span></span>
<span class="line"><span style="color:#24292E;">            decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">              labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;用户名&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">              hintText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;用户名或邮箱&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">              icon</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Icon</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Icons</span><span style="color:#24292E;">.person),</span></span>
<span class="line"><span style="color:#24292E;">            ),</span></span>
<span class="line"><span style="color:#24292E;">            </span><span style="color:#6A737D;">// 校验用户名</span></span>
<span class="line"><span style="color:#24292E;">            validator</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> (v) {</span></span>
<span class="line"><span style="color:#24292E;">              </span><span style="color:#D73A49;">return</span><span style="color:#24292E;"> v</span><span style="color:#D73A49;">!</span><span style="color:#24292E;">.</span><span style="color:#6F42C1;">trim</span><span style="color:#24292E;">().isNotEmpty </span><span style="color:#D73A49;">?</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">null</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;用户名不能为空&quot;</span><span style="color:#24292E;">;</span></span>
<span class="line"><span style="color:#24292E;">            },</span></span>
<span class="line"><span style="color:#24292E;">          ),</span></span>
<span class="line"><span style="color:#24292E;">          </span><span style="color:#005CC5;">TextFormField</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">            controller</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> _pwdController,</span></span>
<span class="line"><span style="color:#24292E;">            decoration</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">InputDecoration</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">              labelText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;密码&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">              hintText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;您的登录密码&quot;</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">              icon</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Icon</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Icons</span><span style="color:#24292E;">.lock),</span></span>
<span class="line"><span style="color:#24292E;">            ),</span></span>
<span class="line"><span style="color:#24292E;">            obscureText</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">true</span><span style="color:#24292E;">,</span></span>
<span class="line"><span style="color:#24292E;">            </span><span style="color:#6A737D;">//校验密码</span></span>
<span class="line"><span style="color:#24292E;">            validator</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> (v) {</span></span>
<span class="line"><span style="color:#24292E;">              </span><span style="color:#D73A49;">return</span><span style="color:#24292E;"> v</span><span style="color:#D73A49;">!</span><span style="color:#24292E;">.</span><span style="color:#6F42C1;">trim</span><span style="color:#24292E;">().length </span><span style="color:#D73A49;">&gt;</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">5</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">?</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">null</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#032F62;">&quot;密码不能少于6位&quot;</span><span style="color:#24292E;">;</span></span>
<span class="line"><span style="color:#24292E;">            },</span></span>
<span class="line"><span style="color:#24292E;">          ),</span></span>
<span class="line"><span style="color:#24292E;">          </span><span style="color:#6A737D;">// 登录按钮</span></span>
<span class="line"><span style="color:#24292E;">          </span><span style="color:#005CC5;">Padding</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">            padding</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">const</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">EdgeInsets</span><span style="color:#24292E;">.</span><span style="color:#6F42C1;">only</span><span style="color:#24292E;">(top</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">28.0</span><span style="color:#24292E;">),</span></span>
<span class="line"><span style="color:#24292E;">            child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Row</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">              children</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">&lt;</span><span style="color:#005CC5;">Widget</span><span style="color:#D73A49;">&gt;</span><span style="color:#24292E;">[</span></span>
<span class="line"><span style="color:#24292E;">                </span><span style="color:#005CC5;">Expanded</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">                  child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">ElevatedButton</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">                    child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Padding</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">                      padding</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#D73A49;">const</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">EdgeInsets</span><span style="color:#24292E;">.</span><span style="color:#6F42C1;">all</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">16.0</span><span style="color:#24292E;">),</span></span>
<span class="line"><span style="color:#24292E;">                      child</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">Text</span><span style="color:#24292E;">(</span><span style="color:#032F62;">&quot;登录&quot;</span><span style="color:#24292E;">),</span></span>
<span class="line"><span style="color:#24292E;">                    ),</span></span>
<span class="line"><span style="color:#24292E;">                    onPressed</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> () {</span></span>
<span class="line"><span style="color:#24292E;">                      </span><span style="color:#6A737D;">// 通过_formKey.currentState 获取FormState后，</span></span>
<span class="line"><span style="color:#24292E;">                      </span><span style="color:#6A737D;">// 调用validate()方法校验用户名密码是否合法，校验</span></span>
<span class="line"><span style="color:#24292E;">                      </span><span style="color:#6A737D;">// 通过后再提交数据。</span></span>
<span class="line"><span style="color:#24292E;">                      </span><span style="color:#D73A49;">if</span><span style="color:#24292E;"> ((_formKey.currentState </span><span style="color:#D73A49;">as</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">FormState</span><span style="color:#24292E;">).</span><span style="color:#6F42C1;">validate</span><span style="color:#24292E;">()) {</span></span>
<span class="line"><span style="color:#24292E;">                        </span><span style="color:#6A737D;">//验证通过提交数据</span></span>
<span class="line"><span style="color:#24292E;">                      }</span></span>
<span class="line"><span style="color:#24292E;">                    },</span></span>
<span class="line"><span style="color:#24292E;">                  ),</span></span>
<span class="line"><span style="color:#24292E;">                ),</span></span>
<span class="line"><span style="color:#24292E;">              ],</span></span>
<span class="line"><span style="color:#24292E;">            ),</span></span>
<span class="line"><span style="color:#24292E;">          )</span></span>
<span class="line"><span style="color:#24292E;">        ],</span></span>
<span class="line"><span style="color:#24292E;">      ),</span></span>
<span class="line"><span style="color:#24292E;">    );</span></span>
<span class="line"><span style="color:#24292E;">  }</span></span>
<span class="line"><span style="color:#24292E;">}</span></span></code></pre></div><p>运行后效果如图3-24所示：</p><p><img src="/assets/3-24.0f814a54.png" alt="图3-24"></p><p>注意，登录按钮的<code>onPressed</code>方法中不能通过<code>Form.of(context)</code>来获取<code>FormState</code>，原因是，此处的<code>context</code>为<code>FormTestRoute</code>的context，而<code>Form.of(context)</code>是根据所指定<code>context</code>向根去查找，而<code>FormState</code>是在<code>FormTestRoute</code>的子树中，所以不行。正确的做法是通过<code>Builder</code>来构建登录按钮，<code>Builder</code>会将<code>widget</code>节点的<code>context</code>作为回调参数：</p><div class="language-dart vp-adaptive-theme"><button title="Copy Code" class="copy"></button><span class="lang">dart</span><pre class="shiki github-dark vp-code-dark"><code><span class="line"><span style="color:#79B8FF;">Expanded</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;"> </span><span style="color:#6A737D;">// 通过Builder来获取ElevatedButton所在widget树的真正context(Element) </span></span>
<span class="line"><span style="color:#E1E4E8;">  child</span><span style="color:#F97583;">:</span><span style="color:#79B8FF;">Builder</span><span style="color:#E1E4E8;">(builder</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> (context){</span></span>
<span class="line"><span style="color:#E1E4E8;">    </span><span style="color:#F97583;">return</span><span style="color:#E1E4E8;"> </span><span style="color:#79B8FF;">ElevatedButton</span><span style="color:#E1E4E8;">(</span></span>
<span class="line"><span style="color:#E1E4E8;">      ...</span></span>
<span class="line"><span style="color:#E1E4E8;">      onPressed</span><span style="color:#F97583;">:</span><span style="color:#E1E4E8;"> () {</span></span>
<span class="line"><span style="color:#E1E4E8;">        </span><span style="color:#6A737D;">//由于本widget也是Form的子代widget，所以可以通过下面方式获取FormState  </span></span>
<span class="line"><span style="color:#E1E4E8;">        </span><span style="color:#F97583;">if</span><span style="color:#E1E4E8;">(</span><span style="color:#79B8FF;">Form</span><span style="color:#E1E4E8;">.</span><span style="color:#B392F0;">of</span><span style="color:#E1E4E8;">(context).</span><span style="color:#B392F0;">validate</span><span style="color:#E1E4E8;">()){</span></span>
<span class="line"><span style="color:#E1E4E8;">          </span><span style="color:#6A737D;">//验证通过提交数据</span></span>
<span class="line"><span style="color:#E1E4E8;">        }</span></span>
<span class="line"><span style="color:#E1E4E8;">      },</span></span>
<span class="line"><span style="color:#E1E4E8;">    );</span></span>
<span class="line"><span style="color:#E1E4E8;">  })</span></span>
<span class="line"><span style="color:#E1E4E8;">)</span></span></code></pre><pre class="shiki github-light vp-code-light"><code><span class="line"><span style="color:#005CC5;">Expanded</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;"> </span><span style="color:#6A737D;">// 通过Builder来获取ElevatedButton所在widget树的真正context(Element) </span></span>
<span class="line"><span style="color:#24292E;">  child</span><span style="color:#D73A49;">:</span><span style="color:#005CC5;">Builder</span><span style="color:#24292E;">(builder</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> (context){</span></span>
<span class="line"><span style="color:#24292E;">    </span><span style="color:#D73A49;">return</span><span style="color:#24292E;"> </span><span style="color:#005CC5;">ElevatedButton</span><span style="color:#24292E;">(</span></span>
<span class="line"><span style="color:#24292E;">      ...</span></span>
<span class="line"><span style="color:#24292E;">      onPressed</span><span style="color:#D73A49;">:</span><span style="color:#24292E;"> () {</span></span>
<span class="line"><span style="color:#24292E;">        </span><span style="color:#6A737D;">//由于本widget也是Form的子代widget，所以可以通过下面方式获取FormState  </span></span>
<span class="line"><span style="color:#24292E;">        </span><span style="color:#D73A49;">if</span><span style="color:#24292E;">(</span><span style="color:#005CC5;">Form</span><span style="color:#24292E;">.</span><span style="color:#6F42C1;">of</span><span style="color:#24292E;">(context).</span><span style="color:#6F42C1;">validate</span><span style="color:#24292E;">()){</span></span>
<span class="line"><span style="color:#24292E;">          </span><span style="color:#6A737D;">//验证通过提交数据</span></span>
<span class="line"><span style="color:#24292E;">        }</span></span>
<span class="line"><span style="color:#24292E;">      },</span></span>
<span class="line"><span style="color:#24292E;">    );</span></span>
<span class="line"><span style="color:#24292E;">  })</span></span>
<span class="line"><span style="color:#24292E;">)</span></span></code></pre></div><p>其实<code>context</code>正是操作Widget所对应的<code>Element</code>的一个接口，由于Widget树对应的<code>Element</code>都是不同的，所以<code>context</code>也都是不同的，有关<code>context</code>的更多内容会在本书后面进阶篇中详细讨论。Flutter中有很多“of(context)”这种方法，读者在使用时一定要注意<code>context</code>是否正确。</p></div></div></main><footer class="VPDocFooter" data-v-6b87e69f data-v-ef5dee53><!--[--><!--]--><div class="edit-info" data-v-ef5dee53><div class="edit-link" data-v-ef5dee53><a class="VPLink link vp-external-link-icon no-icon edit-link-button" href="https://gitee.com/luoguangguang/note/tree/master/docs/largeFrontEnd/flutter/chapter3/input_and_form.md" target="_blank" rel="noreferrer" data-v-ef5dee53><!--[--><svg xmlns="http://www.w3.org/2000/svg" viewbox="0 0 24 24" class="edit-link-icon" aria-label="edit icon" data-v-ef5dee53><path d="M18,23H4c-1.7,0-3-1.3-3-3V6c0-1.7,1.3-3,3-3h7c0.6,0,1,0.4,1,1s-0.4,1-1,1H4C3.4,5,3,5.4,3,6v14c0,0.6,0.4,1,1,1h14c0.6,0,1-0.4,1-1v-7c0-0.6,0.4-1,1-1s1,0.4,1,1v7C21,21.7,19.7,23,18,23z"></path><path d="M8,17c-0.3,0-0.5-0.1-0.7-0.3C7,16.5,6.9,16.1,7,15.8l1-4c0-0.2,0.1-0.3,0.3-0.5l9.5-9.5c1.2-1.2,3.2-1.2,4.4,0c1.2,1.2,1.2,3.2,0,4.4l-9.5,9.5c-0.1,0.1-0.3,0.2-0.5,0.3l-4,1C8.2,17,8.1,17,8,17zM9.9,12.5l-0.5,2.1l2.1-0.5l9.3-9.3c0.4-0.4,0.4-1.1,0-1.6c-0.4-0.4-1.2-0.4-1.6,0l0,0L9.9,12.5z M18.5,2.5L18.5,2.5L18.5,2.5z"></path></svg> 在Gitee上参与编辑此页<!--]--></a></div><!----></div><nav class="prev-next" data-v-ef5dee53><div class="pager" data-v-ef5dee53><!----></div><div class="pager" data-v-ef5dee53><a class="pager-link next" href="./largeFrontEnd/flutter/chapter1/index.html" data-v-ef5dee53><span class="desc" data-v-ef5dee53>Next page</span><span class="title" data-v-ef5dee53>第一章 初识Flutter</span></a></div></nav></footer><!--[--><!--]--></div></div></div><!--[--><!--]--></div></div><footer class="VPFooter has-sidebar" data-v-1919c326 data-v-e03eb2e1><div class="container" data-v-e03eb2e1><p class="message" data-v-e03eb2e1>Released under the MIT License.</p><p class="copyright" data-v-e03eb2e1>Copyright © 2023-present LG of GZU</p></div></footer><!--[--><!--]--></div></div>
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